Protecting color pictures exposed to high humidities against fading and staining



Patented July 28, 1953 PROTECTING COLOR PICTURES EXPOSED TO HIGH HUMIDITIES AGAINST FADING AND STAINING Eugene Scary, Rochester, and Anthony Salerno,

Corona, N .'Y., assignors to Pavelle Color Incorporated, New York, N. Y., a corporation of Delaware No Drawing. Application October 31, 1950, Serial No. 193,304

2 Claims.

The present invention relates to the production of color pictures formed by exposing, developing, and finishing multilayer photographic material, and the object of the invention is to provide a simple and effective process for protecting such a picture from the deteriorating effects of a subsequent prolonged exposure of the picture to high humidity.

The photographic material exposed and developed to produce such pictures, may comprise superposed silver halide emulsion layers, respectively sensitive to light of different colors. Processes of producing such pictures comprise exposure, color forming development, bleaching, fixing, and washing steps. Pictures so produced on some materials fade and develop stains when exposed to high humidity for extended periods. The fading and staining effects of high humidity are augmented by high temperature. Such pictures if unprotected, may be rendered almost useless by an exposure for a few weeks to an atmos phere having a relative humidity and temperature in excess of 90% and 90 F., respectively. Such unprotected pictures may still be in a fair condition after a period of several years, if not subjected to humidities and temperatures higher than are customary in large portions of the temperate zones.

Heretofore, various attempts have been made to protect color pictures from deterioration when exposed to high humidity, but each of those attempts known to us has been open to one or more serious objections.

In accordance with the present invention we effectively protect pictures of the above mentioned character from fading and stain actions during prolonged exposures to high humidity, by subjecting the pictures in the process of their production of a final rinse with a dilute rinse solution containing an alkali which may be borax, and an anti-staining agent which preferably is sodium formaldehyde bisulfite.

m the course of experimental work done by us which led directly to the invention claimed herein, we discovered that in color picture finishing processes, a rather remarkable stabilizing effect on picture dyes adversely affected by high humidity can be obtained by giving the film or other photograph material being processed, a final rinse in a dilute solution of mild alkali, such for example, as borax. While this simple treatment resulted in definite protection against fading of pictures subject to high humidity, it did not protect the pictures exposed to high humidity from objectionable stains.

Eventually, we found, however, that effective protection of color pictures of the above mentioned type, against both fading and staining when exposed during prolonged periods to high humidity, can be substantially prevented, or greatly reduced, by the use of our invention, claimed herein, by giving the pictures in the process of production a final rinse in an aqueous solution containing small amounts of a mild alkali as borax, and an anti-staining agent which may be either a formaldehyde bisulfite or benzotriazole. The use of our present invention is characterized in particular by its effectiveness in preserving color balance and in keeping the highlights of color film and paper substantially free from stain when the finished and dried pictures are subject to high humidity for periods suitably long to practically ruin the pictures if unprotected. The method disclosed and claimed herein is the first one known to us which gives protection against the fading and staining effects of high humidity on color pictures of the above mentioned type.

The Mackey Patent 2,487,569 of November 8, 1949, discloses a process of treating pictures of the above mentioned type, in the process of their production, by a rinsing treatment intended primarily as an anti-staining treatment, but which is said to effect some reduction in the fading of the pictures treated. The treatment disclosed in the Mackey patent does not include or make use of our invention, and we have found that it is not. effective for providing satisfactory protection against the fading of color pictures exposed to high humidity. Moreover, our rinse material is of a more stable character and is easier to prepare than the Mackey patent material, and has no resinous characteristics which add to the dimculty in drying film or print pictures treated with the rinse material, when the rinsing treatment forms part of a continuous process of producing pictures. Moreover, the anti-fading and antistaining agents included in our rinse are definitely less expensive, and can be used in smaller quantities, than the special treating agents included in the Mackey patent rinse material.

The photographic layer materials which may be protected against the fading and staining effects of high humidity by the use of the present invention include color reversible film, color negative film, color reversible or negative printing material coated on an opaque white base, and color positive paper material. The present invention may be used equally well when the color images are produced with color formers included in the 3 emulsion, and when they are produced by the use of developers containing color formers and developing agents.

In the preferred practical mode of use of our invention,.we employ a final rinse bath consisting of water to which is added from 1-7% of formaldehyde bisulfite, and borax varying in amount from .5% up to the amount required to saturate the solution. In practice, we have found'that a rinse containing a 1% solution'of formaldehyde bisulfite and a solution of borax requires about ten minutes immersion of the color picture treated, to obtain the maximum protective effect, and have found that doubling the concentrations reduces the required immersion time approximately 50%. While the protective effect obtained is not believed to be a linear function of the bisulfite and borax solution concentrations,"

it is believed that the relation of the concentrations to protective effect are approximately linear.

However, objectionable crystallization develops when concentrations are unduly increased. Specifically, we have found that when the formaldehyde bisulfite concentration is higher than about 4% and the borax concentration is higher than about 1 the color material treated will dry with salts and a greasy-like substance on its surface. The substances thus deposited on the dried color material can be readily removed by a short water rinse or spray. Increasing the concentration increases the amount and cost of the chemicals used. For practical purposes, we have found that optimum results are ordinarily obtained when use is made of a 2% solution of formaldehyde bisulfite and a 1% solution of borax is used. However, we have obtained excellent results with concentrations of formaldehyde bisulfite varying from 17% and of borax varying from .5% to saturation, provided suitable allowances are made for the tendency to crystallization deposits on the dried color material when the bisulfite and borax concentrations are greater than about 2% and 1%, respectively.

Although we have found that the anti-staining effects of benzotriazole and formaldehyde bisulfite are substantially equal, we prefer to use the latter as an anti-staining agent because it is substantially less expensive, particularly if the formaldehyde bisulfite is made as the final rinse bath is prepared. By adding formaldehyde to a solution of sodium bisulfite, sodium formaldehyde bisulfite is quantitatively produced. To'complete the bath it is necessary merely to dissolve a wetting agent and alkali in the solution. According to our present knowledge and belief, we may use in our process any alkali agent known to us. However, we consider mild alkalies such as borax and sodium carbonate and phosphates, to be much preferable to a stronger alkali such as sodium hydroxide.

This application is a continuation in part of ourprior application Serial No. 158,162, filed April 27, 1950, now abandoned.

While in accordance with the provisions of the statutes, we have illustrated and described the best form'of embodiment of our invention now known to us, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of our invention as set forth in the appended claims and that in some cases certain'features of our invention may be used to advantage without a corresponding use of other features.

Having now described our invention, what we claim as new and desire to secure by Letters Patent, is:

1. In a processfor producing color photographic images in silver-halide emulsions by exposing the emulsions, color-forming developing the same, bleaching, fixing, rinsing and drying, the improvement which comprises prolonging the life of the image especially when stored under relatively high humidity and temperature conditions by modifying said rinsing step to include rinsing of the said emulsion with an aqueous solution containing from 1% to 7% of an alkali formaldehyde-bisulphite and containing borax from 0.5% up to the amount required to saturate said solution.

2. In a process for producing color photographic images in silver-halide emulsions by exposing the emulsions, color-forming developing the same, bleaching, fixing, rinsing and drying, the improvement-which comprises prolonging the life of the image especially when stored under relatively high humidity and temperature conditions by modifying said rinsing step to include rinsing of the saidemulsion with an aqueous solution containing about 2% of an alkali formaldehyde bisulphite and about 1% of borax.

EUGENE SEARY. ANTHONY SALERNO.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,313,523 Donovan Mar. 9, 1943 2,367,516 Muehler Jan. 16, 1945 2,475,134 Harsh July 5 ,1949 2,487,569 Mackey Nov. 8, 1949 2,490,760 Henn Dec. 6, 1949 2,518,686 Harsh Aug. 15, 1950 

1. IN A PROCESS FOR PRODUCING COLOR PHOTOGRAPHIC IMAGES IN SILVER-HALDE EMULSIONS BY EXPOSING THE EMULSIONS, COLOR-FORMING DEVELOPING THE SAME, BLEACHING, FIXING, RINSING AND DRYING, THE IMPROVEMENT WHICH COMPRISES PROLONGING THE LIFE OF THE IMAGE ESPECIALLY WHEN STORED UNDER RELATIVELY HIGH HUMIDITY AND TEMPERATURE CONDITIONS BY MODIFYING SAID RINSING STEP TO INCLUDE RINSING OF THE SAID EMULSION WITH AN AQUEOUS SOLUTION CONTAINING FROM 1% TO 7% OF AN ALKALI FORMALDEHYDE-BISULPHITE AND CONTAINING BORAX FROM 0.5% UP TO THE AMOUNT REQUIRED TO SATURATE SAID SOLUTION. 